Install Package should add a Node to AddonRootCategories

#### Purpose

1. Fixed some errors connected with adding nodes to incorrect collection (to BrowserRootCategories instead of AddonRootCategories).
2. Fixed installing package process for dlls. Now if DLL is a part of package it is added to AddonRootCategories.

#### Modifications

Added new parameter to `DynamoLoader.LoadNodesFromAssembly` which points to `ElementType` of assemblies types. It is necessary for NodeModel libraries.

For ZeroTouch libraries loading process is different. So was decided to add prefix to library path and later using this prefix is decided which `ElementType` library types should have.

#### Additional references

[MAGN-4720](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4720).

#### Reviewers

@aosyatnik, @Benglin please, take a look.