Improve remote path mapping

[joonty]

Add features for remote path mapping:

• Allow regular expressions for remote path mapping
• GUI style interface for managing multiple path maps, as Vim dictionary is cumbersome
• Remove path maps from options dictionary, have separate dictionary

[hobbes3]

Also adding remote root path doesn't work on Vdebug. For example, this doesn't work:

let g:vdebug_options = {
\   'path_maps': {
\       "/": "/Users/hobbes3/mounts/nead",
\   },
\}

Instead I have to do something like this:

let g:vdebug_options = {
\   'path_maps': {
\       "/var/www/vhost": "/Users/hobbes3/mounts/nead/var/www/vhost",
\   },
\}

[joonty]

@hobbes3 thanks for that!