Increase readability in adbfs.cpp

Bring consistency to improve readability, make several small optimizations in memory and method calls, remove redundant code, fix some small bugs. Also removed `adb_push_pull_cmd()` in favor of separating the two separate functionalities into their more logical (and already-existing) counterparts.
Merge pull request #13 from impinball/patch-2

Increase readability in adbfs.cpp