Manual , documentation update V2.2

Describes the new features and changes of WG++ V2.1.10

New in this issue:

• Chapter 4.6.2 is completely rewritten and is now called 'Conditional operations and arguments' It explains:
- the newly introduced ‘boolean operators’ & (and) | (or) ^ (xor) and ! (not)
- the RPN style ‘boolean expressions’ in chapter 4.6.2.3
- and the new statements ‘if’ and ‘else’ in chapter 4.6.2.4.3
• New chapter 4.4.1.1.1 'Headersets' and 4.4.2.3.1 'Subpage header list' explaining headersets and their use in subpages
• Revised chapter 4.6.4.5.3 'Date and time calculations' to reflect the changed definition of numeric timespan input values and the format argument
• Revised chapter 4.6 'Operations', details of arguments used in operations moved to the chapters where the operations are explained for which they are relevant.
• New chapter 4.1.1 'SiteIni header'
• 3 new readonly elements added in chapter 4.5.4 'Read_only elements' and APPENDIX C