Bring PEX, ADC, and DAC into the fold

[siddMahen]

Bruno already did the hard work of separating these features onto their own branches.

Once we can start running functional tests on the boards, we should test and merge into master.

[siddMahen]

@brunofalmeida @vogeldylan All that's left to do is run tests using the new interfaces, make sure they still work, and cleanup the commit history.

• ADC (#63)
• PEX
• DAC

[siddMahen]

As of #66, #67 and #63 this is all done!