deprecate `create_report` in favor of `render_template` and expose it on book, too

[fzumstein]

Current situation:

xw.pro.reports.create_report()
myapp.create_report()
mysheet.render_template()

Suggestion:

xw.pro.reports.render_template()  # same as next line, but doesn't require to start with an app object
myapp.render_template()  # copies template book, then renders all sheets in copied book
mybook.render_template()  # renders all sheets in book
mysheet.render_template()  # renders single sheet