Switch to less.js-windows instead of dotLESS.

dotLESS seems to be buggy, especially when using lots of
nested @import statements.
Cache the results of LESS file compilation.

Should speed up builds with complex LESS file substantially.
PEP8 formatting cleanup.

Fixes #64.
Remove unneeded backup file from PyCharm project version upgrade.
Add Global Links plugin.
Merge experimental/replace_dotless
Update less.js-windows.
Fix cache invalidation problems.
Expose simple way to get a plugin's name.