Navdrawer updates

[damyanpetev]

Changes for #447:

Additional information related to this pull request:

• Rename <ig-nav-drawer> to <igx-nav-drawer> ( ⚠️ )
• Add active pinThreshold on window resize and two-way bind [(pin)] to go with that.
• Export IgxNavigationModule from main source. Not sure this is the best way, directives can be merged in the existing module.
• Drawer closes (when not pinned) when you select a sample
• Misc cleanup of unused imports

Edit: The active pinThreshold actually introduces another change ( ⚠️ ) as it will override the pin setting. Could remove the default threshold or separate them internally to allow the pin option to override instead?

[coveralls]

Coverage increased (+0.05%) to 91.018% when pulling 7274eda on damyanpetev:navdrawer-updates into f4e479a on IgniteUI:master.

[coveralls]

Coverage increased (+0.05%) to 91.018% when pulling 74266df on damyanpetev:navdrawer-updates into f4e479a on IgniteUI:master.

[coveralls]

Coverage increased (+0.05%) to 91.018% when pulling db3b7cf on damyanpetev:navdrawer-updates into f4e479a on IgniteUI:master.