implement isHidden/setHidden for fs without 'hidden' attribute
don't reflect file changes into path-based functions until flush/close
move exists/isDirectory checks into native listImpl to improve perf

Moving the exists/isDirectory checks into the native listImpl method
required modifying the fs.list implementation to distinguish between
those two states when calling its callback with results.  So I added
an error parameter to its callback, and I made it the first parameter,
per the nodejs convention.

And that entrained changes to the fs init/test code, at which point
I realized that we're testing the initialization of old db versions
unnecessarily, since what really matters is whether those old versions
can be upgraded to the latest one while retaining the fidelity
of the files.

And testing old db versions as the fs interface changes would require
writing a bunch of mostly-duplicate, obsolete code.  So I updated the fs
init/test scripts not to test old versions (until after upgrading them).
determine if isDir in fs.list; measure perf w/JVM.monotonicTimeMillis
Merge branch 'master' into optimize-file-connection

Conflicts:
	tests/automation.js
ensure close without changes doesn't update mtime
Merge branch 'master' into optimize-file-connection
don't truncate file when opening output stream; add midlet to test mtime changes
Merge branch 'master' into optimize-file-connection
Merge branch 'master' into optimize-file-connection

Conflicts:
	tests/automation.js
Merge pull request #771 from mykmelez/optimize-file-connection

fix various fs correctness and perf issues
Merge branch 'master' into export-import-fs

Conflicts:
	libs/fs.js
	tests/automation.js
	tests/fs/automation.js