Add signature plugin back to CORE_PLUGINS (palantir#83)

* Add signature plugin back to CORE_PLUGINS

* Alphabetize imports and plugins listing

Reverse urlencoding (palantir#81)

Unquote parsed urls in both Workspace and Document (palantir#80)

* unquote parsed urls in both Workspace and Document

* Also unquote path used for syspath lookup

* Add test ensuring chars are urldecoded when setting Workspace/Document path

* Unquote before parse, remove unneeded import

* Lint fix

Correct format_document (palantir#74)

Check not dirty

Fix script

Fix signatures as per https://github.com/palantir/python-language-ser…

…ver/pull/41/files (palantir#49)

Support python projects in subdirectories (palantir#34)

* Create test for non-root syspath

* Implement syspaths