Clean up/improve lift-common Scaladocs.

Some places get more detailed Scaladocs, others get some facelifts and get
converted to wiki syntax instead of HTML. Examples added throughout.
Move an import up to the head of Conversions.scala.
Clean out documentation that adds nothing.

Some of the scaladocs were extremely redundant with respect
to the functions they were describing. This commit drops
those Scaladocs.
Deprecate NodeSeqFunc.

It doesn’t seem to be used anywhere and we generally lean
on transformation functions rather than generation functions
for NodeSeq. This is also something we want to continue to
encourage, so making using NodeSeqs directly a little more
painful is okay.
Rename a variable in Logger.

checkConfig was used to make sure setup was being run. It’s
now named ranSetup, since that’s more reflective of what it
means.
Use UnsupportedOperationException where reasonable.

SimpleList and SimpleVector have a bunch of unsupported
operations with respect to regular Java collections; these
were through Exception instances. We switch them to throw
UnsupportedOperationException as per the Java collection
contract.