Extracted Replacer interface and moved replacers to a separate package.
More advanced Text pattern that will take quotes into account.

A more advanced pattern that tries to take quotes into account. In case
this pattern does not work, this commit can be reverted and instead a
simpler pattern is used that relies on html tags being opened and closed
with < and > brackets. It assumes that < and > are always part of HTML
tags so any textual (content) occurrence should be replaced with html
entities (escaping).