Delete blob improvement

* Created ROpenFLUID function deleteSimulationBlob
* Fixed R-side pointer finalizing

(references OpenFLUID/openfluid#942)

Delete blob improvement

* Created ROpenFLUID function deleteSimulationBlob
* Fixed R-side pointer finalizing

(references OpenFLUID/openfluid#942)

Fix of non void functions with no return

(closes OpenFLUID/openfluid#895)

Update of OpenFLUID logo

C++14 compliance

Update of build process on Windows systems

Extension of the validity of the semicolon separated strings arguments

* Extended validity of the paths argument in addExtraSimulators-
ObserversPaths to R vectors
* Extended validity of the unitid and varname arguments in
addVariablesExportAsCSV to R vectors

(closes OpenFLUID/openfluid#726)

Add of optional arguments to addVariablesExportAsCSV

* Added optional argument unitid for one selected unit in unitclass
* Added optional argument varname for selected variable(s)
* Added optional argument precision for outputs digits number
* Updated tests to match new developments

Improvements on package check and build process

* Added --as-cran mode on checking process to check against CRAN
  submission requirements
* Improved DESCRIPTION content to meet the CRAN submission requirements
* Updated README
* Cleaned CMake script files

Update of documentation

* Refactored build system for documentation
* Updated main description
* Fixed some broken links in functions descriptions