PyDMChannel is broken for filter syntax and some symbols (like #) in CA

[flowln]

Describe the bug
Previous to version 1.19 of PyDM, you could use the CA filter syntax in PyDM channels in order to do some cool stuff, like get a specific value from a waveform record using the (pv).[index] syntax. With the change to use urlparse in 2a55563, this was broken, and now an Exception is raised here when trying to use it.

Steps to Reproduce
Try to connect to a waveform record specifying the index via the filter syntax.

Possible Solution
Revert to not using urlparse, since a CA address may not always be a valid URL.

[flowln]

On an unrelated incident, I found out that the code change talked about here also makes PyDMChannelunable to handle some symbols in CA addresses, notably the # symbol. In this case, I have a PV called <...>:DBG#HOMING, that doesn't connect, and on the connection inspector, shows up only as <...>:DBG.

This one could more easily be solved by setting allow_fragments to False in the urlparse call.