Extend whitespace/newline removal support

[darnocian]

There is some support for removal of whitespace / newlines using options on the context and using tags <| and |>. However, this is still not flexible enough.

Proposal is to deprecate the current behaviours, and to extend the open / closing script tag sequence using - and *.

<%- would strip any whitespace to the left to the start of the current line. -%> would strip any whitespace to the right to the end of the current line. <% would strip any whitespace and new lines to the left until the first non-whitespace character is reached. %> would strip any whitespace and new lines to the right until the first non-whitespace character is reached.

e.g.

     <%- if cond %>
         <%* value %>
     <%* end *%>

[darnocian]

lexer already updated on the whitesplate_trim_improvements branch. the streamwriter needs to be updated:

• the buffer needs to keep all whitespace until it is known what to do with it. This is for the stripping to the left behaviour.
• stripping to the right will need a state variable