Improve formatting of long lines

Automatically wrap long lines in paragraphs and in lists.

Improve pretty-printing of tabular data

Columns are now vertically aligned, and columns that contain integer values only are right-aligned.

Example pretty-printed table:

   sales:: Vehicle Sales

       | year | type  | quantity
       | 2010 | sedan |    10000
       | 2011 | SUV   |     2000
       | 2020 | any   |      500

Improve stability and usability

Add support for nested lists.
Allow #, * and = unescaped in paragraphs text.
Emit identifiers and references in XML serialization.
Emit code blocks in XML serialization.
Allow tables to have arbitrary white space at the beginning of the line - so | can be aligned when conditions are present.

Small fixes to XML export tool

v0.2.3

Update documentation; add build instructions

Improved generating of XML documents

v0.2.2

Output correct entities for special symbols

Preserve whitespace before punctuation

v0.2.1

Preserve presence/absence of whitespace before punctuation

Pretty-print and enforce complex conditions

v0.2.0

Add support for combined conditions (and/or)

Generate compliant DocBook XML

Improve documentation on how to generate and validate the DocBook output.

Add an example of generating DocBook

v0.1.8

Add an example of generating DocBook from SAMx

General support for conditions

Greatly improve the robustness of the condition parsing and processing.

In addition to variable=value conditions, support variable in {set, of, values} conditions as well.