Misc fixes (elm support)

[mworrell]

Description

Fixes:

• new site setup: copy skeleton crashes
• new site not started after skeleton copy and db install
• first serve of lib files using 'file' crashes cowboy http2 handlers

Checklist

• documentation updated
• tests added
• no BC breaks

[mworrell]

Error log during first serve of lib files.

11:28:18.315 [error] at: "cowmachine:request_1:103", class: error, code: 500, dst: #{ip4 => "127.0.0.1",port => 8443}, in: cowmachine, level: error, path: <<"/lib/bootstrap/css/bootstrap~bootstrap-base-site~/css/jquery.loadmask~z.icons~z.growl~z.modal~z.icons~site~3207938627.css">>, reason: {badfun,{{file,147502,<<"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/zotonic_mod_bootstrap/priv/lib/bootstrap/css/bootstrap.css">>},#Fun<z_file_request.8.32982794>}}, src: #{ip4 => "127.0.0.1",port => 55125}, stacktrace: [{cowmachine_response,'-send_response_bodyfun/4-fun-4-',2,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine_response.erl"},{line,126}]},{cowmachine_response,send_response,1,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine_response.erl"},{line,58}]},{cowmachine,request_1,5,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine.erl"},{line,76}]},{cowmachine,request,2,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine.erl"},{line,57}]},{cowboy_stream_h,execute,3,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,296}]},{cowboy_stream_h,request_process,3,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,274}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}], text: "Unexpected exception"
11:28:18.315 [error] cow_http2_machine:1082 CRASH REPORT Process <0.4301.0> with 1 neighbours crashed with reason: no match of right hand value {stream,69,<<"GET">>,nofin,12582912,{[],[]},0,undefined,fin,65535,0,0,<<"trailers">>} in cow_http2_machine:prepare_headers/5 line 1082
11:28:18.315 [error] Ranch listener zotonic_https_listener_ipv4 terminated with reason: {badmatch,{stream,69,<<"GET">>,nofin,12582912,{[],[]},0,undefined,fin,65535,0,0,<<"trailers">>}}
11:28:18.532 [error] at: "cowmachine:request_1:103", class: error, code: 500, dst: #{ip4 => "127.0.0.1",port => 8443}, in: cowmachine, level: error, path: <<"/lib/js/modules/jstz.min~/cotonic/zotonic-wired-bundle~/js/apps/zotonic-wired~z.widgetmanager~/js/modules/z.notice~z.imageviewer~z.dialog~z.clickable~livevalidation-1.3~jquery.loadmask~/bootstrap/js/bootstrap.min~/js/modules/responsive~1022649148.js">>, reason: {badfun,{{file,12200,<<"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/zotonic_mod_l10n/priv/lib/js/modules/jstz.min.js">>},#Fun<z_file_request.8.32982794>}}, src: #{ip4 => "127.0.0.1",port => 57001}, stacktrace: [{cowmachine_response,'-send_response_bodyfun/4-fun-4-',2,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine_response.erl"},{line,126}]},{cowmachine_response,send_response,1,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine_response.erl"},{line,58}]},{cowmachine,request_1,5,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine.erl"},{line,76}]},{cowmachine,request,2,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowmachine/src/cowmachine.erl"},{line,57}]},{cowboy_stream_h,execute,3,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,296}]},{cowboy_stream_h,request_process,3,[{file,"/Users/marc/Sites/mqtt/zotonic/_build/default/lib/cowboy/src/cowboy_stream_h.erl"},{line,274}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}], text: "Unexpected exception"
11:28:18.532 [error] cow_http2_machine:1082 CRASH REPORT Process <0.4768.0> with 0 neighbours crashed with reason: no match of right hand value {stream,17,<<"GET">>,nofin,12582912,{[],[]},0,undefined,fin,65535,0,0,<<"trailers">>} in cow_http2_machine:prepare_headers/5 line 1082
11:28:18.532 [error] Ranch listener zotonic_https_listener_ipv4 terminated with reason: {badmatch,{stream,17,<<"GET">>,nofin,12582912,{[],[]},0,undefined,fin,65535,0,0,<<"trailers">>}}