The cli tool parses the provided strings.xml files and pushes them
to CDS. Before this update, it left special characters such as new lines, tabs,
multiple spaces, single or double quotes etc untouched.

With this update the, the behavior of Android's XML parser is followed as
outlined here:  https://developer.android.com/guide/topics/resources/string-resource

The exact mechanics  have been documented in StringXMLConverter#unescapeJavaString().

When `TxNative#setSupportSpannable()` is disabled, the SDK used to perform only these
conversations:
*  "&lt;" to  "<"
*  "&gt;" to  ">"
Now it also performs the following:
*  "&amp;"  to "&"
This functionality has been moved to  `Utils#unescapeHTMLEntities()` .

When `TxNative#setSupportSpannable()` is enabled, it no longer passes all strings through
`fromHTML()`. If the string contains no spans, it is passed through `Utils#unescapeHTMLEntities()`
as usual. This is to preserve new lines and multiple spaces, which `fromHTML()` removes.

The app has been updated to contain a string with HTML markup. It's not rendered stylized
by default. In MyApplication.java, the setSupportSpannabled() has to be commented in.

The readme has been updated to include a section regarding string styling.

Unit tests have been added to cover all cases in txsdk and cli modules.