Buddy to install OpenFLUID examples

* Added example buddy, including basic functionalities 
  for installing examples
* Updated buddies tests
* Added RuntimeEnvironment entries for examples
* Cleaned buddies source code

(references #20, references #80)
Rename and move Builder descriptor classes

* Moved Builderxxx from guicommon to fluidx namespace
* Renamed Builderxxx to AdvancedxxxDescriptor
* Moved GeneratorSignature and FunctionSignatureRegistry from guicommon to ware namespace
Change management of Observers signatures and check

* Created an ObserverSignatureRegistry class to store Observers plugin signatures
* Created a WaresHelper class to perform checks on Monitoring plugin files
Move Function plugins checking to WaresHelper
Refactor FunctionSignatureRegistry

* Made FunctionSignatureRegistry update himself in constructor, avoiding some explicit updates
* Removed FunctionSignatureRegistrySub class, thaht was used for tests but is no more useful
* Used of built-in example functions as default functions for FunctionSignatureRegistry test cases
Change return parameter of WaresHelper check functions

* Monitoring and Model plugins checking now fill a list of missing IDs, instead of a textual list
Refactor relations management in AdvancedDomainDesc

* Added check of Unit relations when adding a Unit to the domain
* Made const the access to Unit relations to forbid direct modifications
* Added functions to add or remove a relation between two Units, and clear all relations of a Unit with others
Changed threw messages from Builder to Framework
Remove unused "Run" section of project explorer

* Moved run information under "Simulation" section
Merge branch 'rearrange-project-explorer' of https://github.com/alibres/openfluid into alibres-rearrange-project-explorer