Toolkit should use Expression builder

[skendrot]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  <!-- Please search GitHub for a similar issue or PR before submitting -->
[x] Feature request <!-- Please file a UserVoice request and include the link below https://wpdev.uservoice.com/forums/110705-universal-windows-platform/category/193402-uwp-community-toolkit -->
[ ] Sample app request
[ ] Documentation issue or request
[ ] Question of Support request => Please do not submit support request here, instead see https://github.com/Microsoft/UWPCommunityToolkit/blob/master/contributing.md#question

UserVoice link

Current behavior

The toolkit currently uses expressions that are stringly typed. The toolkit should use the new expression builder classes. Using the classes would also help others see how they can be used.

Expected behavior

To use the expression builder classes

Minimal reproduction of the problem with instructions

Environment

Nuget Package(s): 

Package Version(s): 

Windows 10 Build Number:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [ ] Insider Build (xxxxx)

App min and target version:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [ ] Insider Build (xxxxx)

Device form factor:
- [ ] Desktop
- [ ] Mobile
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [ ] 2017 15.3
- [ ] 2017 15.4