Release for review of initial development

• support for connections handling replacing interfaces
• support for variables handling for setting layer paths
• support for clayer, cimage, cproject and csolution elements in PDSC​
• added --no-update-rte flag to skip the update of RTE folder contents in csolution
• added list layers command for finding layers with compatible connections
• added list toolchains command for finding configured toolchains
• added top level misc node handling​ in cdefault
• added for-context and not-for-context keywords replacing for-type and not-for-type
• accept command line input *.csolution.yml without explicit -s,--solution flags