Fix PMD warnings in swap code

Opening an issue instead of fixing them myself since they are non-trivial (already did the trivial ones) and I'd rather have someone who wrote or reviewed the code fix them.

AndroidXMLDecompress.java:118:  Avoid using a branching statement as the last in a loop.
localrepo/SwapService.java:569: These nested if statements could be combined
localrepo/peers/BluetoothPeer.java:33:  Ensure you override both equals() and hashCode()
localrepo/peers/BonjourPeer.java:31:    Ensure you override both equals() and hashCode()
net/LocalHTTPD.java:268:        Check the value returned by the skip() method of an InputStream to see if the requested number of bytes has been skipped.
net/bluetooth/BluetoothServer.java:306: Check the value returned by the skip() method of an InputStream to see if the requested number of bytes has been skipped.
views/swap/SwapWorkflowActivity.java:745:       Do not use if statements that are always true or always false

These are the only warnings left to enable java-basic in PMD, which is pretty important.

CC @eighthave @pserwylo