Remove t/logger/file.t as it does nothing useful
Add test for Logger::File log_dir attribute
move test to proper location
Add environment and config_location into logger options.
Remove $app from Dancer2::Logger::File + bugfix

The environment and location attributes are now required and are
provided by the Dancer2::Core::App's _build_logger_engine. This way the
default values of these attributes, which were using $_[0]->app are
removed (as app does not exist inside D2::L::File)

Also the log_dir's trigger method is extracted into it's own. This
allowed the addition of a BUILD method, which calls this extracted
trigger method, which checks the existence of the log_dir (and also
attempts to create it otherwise). Before this fix this check was NOT
executed, when the log_dir was built using _build_log_dir (as the
builder method does not trigger the trigger method).
Move the log_dir test into the attribute isa check, add test:

No need for BUILD, no need for triggers. An attribute already has
a way to check if the value is okay.

Added another test to see it properly creates the directory.
refactor, cleanup, give test descriptions
reflect changes
Merge branch 'issue/logger_file_default_dir'