Implemented support for Nimble local cache with package directories with
a checksum of the package at the end of their names. Now the compiler
supports package paths in the form:
* /path_to_nimble_cache_dir/pkgs/package_name-1.2.3-
FEBADEAEA2345E777F0F6F8433F7F0A52EDD5D1B
* /path_to_nimble_cache_dir/pkgs/package_name-#head-
042D4BE2B90ED0672E717D71850ABDB0A2D19CD2
* /path_to_nimble_cache_dir/pkgs/package_name-#branch-name-
DBC1F902CB79946E990E38AF51F0BAD36ACFABD9
Related to nim-lang/nimble#127
This solves two issues:
1. Some notes were enabled explicitly for some verbosity levels, so
--hintName:on has no effect if verbosity level was too low.
2. Verbosity level for notes is not longer scattered across the source code,
instead if now lives in msgs.nim NotesVerbosity array
3. Individual note settings have stronger effect than verbosity setting,
so --hintName:off will disable hint regardless of high verbosity setting,
and vice-versa --hintName:on will enable hint even on low verbosity setting.