update to SQLCipher v3.1.0

refs #3663 https://dev.guardianproject.info/issues/3663
purge guava-r09.jar, sqlcipher no longer needs it

refs #3663 https://dev.guardianproject.info/issues/3663
Eclipse: set libs/ as default jar location

refs #3663 https://dev.guardianproject.info/issues/3663
Eclipse: the test/sample projects expect the lib project at "cachewordlib"
include static encodeHex() method to purge commons-codec.jar

cacheword needs to have as few deps as possible, so purge this jar.  Thanks
to sqlcipher:

https://github.com/sqlcipher/android-database-sqlcipher/commit/817cff171c99bf6dfc654df3658dbb8af0d59e25

fixes #3663 https://dev.guardianproject.info/issues/3663
point to Android SDK for javadoc for android-support-v4.jar

If you have your Android SDK installed at /opt/android-sdk, then this will
make Eclipse automatically use the SDK's docs for the javadoc for methods
from the Support library.
replace heavy KDF iteration count function with one based on /proc/cpuinfo

The previous KDF iteration count measuring method took a long time to run
and depended on including spongycastle.  In the interest of keeping the
library as minimal as possible, it is good to remove dependencies.  In the
interest of usability, calculating the iteration count should be very fast.

fixes #3146 https://dev.guardianproject.info/issues/3146
fixes #3665 https://dev.guardianproject.info/issues/3665
fixes #492 https://dev.guardianproject.info/issues/492