Collection directory name

[havatv]

Use the pathvalidate package to sanitise collection names in order to use them as collection directory names. We want the collection names to be a part of the collection directory names because the user will see these names when looking for collection SVGs in the QGIS GUI.
Since pathvalidate is not a standard package, version 2.2.2 has been included in the ext_libs directory.

Fixes: #110

The collection directory will now be a combination of the sanitised collection name and the sanitised repository name.
Example: Animal silhouettes (Alina's Repository).

An alternative is to use a combination of the santised collection name and a hash.
Example: Animal silhouettes-33b75e8e0ac1ef736eae109d5d5de0697f4b2174.

If this PR is applied, previously installed collections will have their directories renamed, so the user may have to update QGIS projects that use/include resources from these collections.

What has been done to make the transition smoother for the users:

• When looking up a collection that is already installed, the collection directory is renamed
• Calling local_collection_path in rebuild_collections (repository_manager.py) - will rename already "installed" collections.