Add support for excluding directories on other volumes, at least from
Android Q onwards.
Previously, Auxio only supported excluding the primary volume. This was
mostly out of laziness, as the excluded directory implementation was
shamelessly copied from Phonograph. This commit completely refactors
the excluded directory system, dumpstering the old database (which was
overkill anyway) for a new system based on SharedPreferences that is
actually capable of handling external volumes.
Now, limitations regarding external volumes still apply below Android
Q, as the VOLUME_NAME field does not exist on those versions. However,
this should resolve at least one major complaint regarding the
excluded directory system. Now theres just all of the other complaints.
Resolves#134.
f3a7813f5e