Revert "Make it possible to grab a node if the value, a sentence, starts with the node."

This reverts commit 523b17a06063b904b3474a9e80b21ca3b7c06eaf.
Revert "Don't remove the node when iterating through the nodes."

This reverts commit 2ad5811cdb7ee49317e08deb4a4406ef77ab9085.
Revert "Remove old debugging line."

This reverts commit 7e8d3a636a7916e64d5f76242159643dff1356da.
Revert "Added getNode(String value) to YamlManager to get the node of a value."

This reverts commit 541c7229a518ef3a47283c0b9983733cd0f5d413.
Extracted ValueHolder from DataField.
Added snakeyaml to dependencies
Rewrote YamlNode
More work on ValueHolders - added getters with default
More work on YamlNode:
* treat SnakeYaml's output as read-only
* added more children-adding methods
* added node-counting methods
Random fixes and javadocs.
Overhauled YamlManager to use SnakeYaml and the new YamlNode
Added YamlCombiner
Added getFinalNodeCount() to YamlManager
Random fixes and javadocs.
Fixed one NPE in YamlNode
Fixed some bugs in ValueHolderBase and made some fields private.
Fixed some bugs in YamlNode, improved Settings
Fixes in SimpleYamlManager, YamlManager and YamlCombiner.
* not loading the yaml in manager's constructor anymore
* YamlCombiner.setLoggingManager() now sets the logger for all the
sub-YamlManagers
* fixed byte array to number conversions
* other minor fixes
Added Mockito dependency. Added new unit tests and improved existing.
Added missing license headers.