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[processing] fix help file generator
[processing] fix parameter names in TauDEM algorithms
Fix Qt5 build
Http request/response handler refactoring.

HTTP Request handler now manages HTTP request and response.

* added methods to manage HTTP response headers
* added methods to manage response body
* added accessors API methods for request parameters and
  response headers and body
Removed python plugins define
Add plugin files and define
Added env var for custom plugin directory
Added define for conditional server plugins compilation
Added python server plugins
Added serve python plugins
Added serve python plugins
Added getEnv to plugins API
ASTYLE Formatted
Comments added
Fixes wrong number of bytes logged when debug activated.

Funded by ItOpen - QGIS Borg - Resistance Is Futile
Added comments for bindings.
Expose response body and infoFormat
Allow body clear
Set exception moved to public