Adds configuration variables, TPL and TMP, for RainTPL

The path for templates and temporary files are now part of the configuration.

For a custom install, it's possible to put these writable directories elsewhere than in the read-only source code.
Removed redundant check on RAINTPL_TMP directory

The same test is already on line 93
Adds empty directories: cache, data, pagecache and tmp. Removes mkdirs.

They are still in .gitignore because their future content will still be ignored.
Removes htaccess file creation and adds them in the repository

I also removed the previously created placeholders, which after all, have no more utility.
Merge pull request #11 from Sbgodin/rainVariables