Add erl-log module

* Add logging functionality modelled after yasnippet logging
erl-otp: Rename functions

* Rename functions to verb form
* Make erl-index.el use variable instead of function call
erl-otp: Add defvars for paths
erl-otp: Rework path finding functions
erl-otp: Refactor delimiters, docs and vars
erl-otp: Refactor shell path functions

* Remove unit tests