Extend clayers element with 'path' and 'copy-to' attributes

[ReinhardKeil]

Proposed changes to clayer element:

• There should be additional attributes that copy layers.

Attribute	Description	Type	Use
path	Path to the directory that contains the layer	xs:string	required
file	Name of the *.clayer.yml file (optional with relative path to the directory specified with path)	xs:string	required
copy-to	Path that used to copy the layer into the csolution project (default is attribute path)	xs:string	optional

• Change the parent element to <csolution> as this can also store templates (see #306)
• Remove as there is already a description: node in the *.clayer.yml file.

Examples:

<csolution> 
  <clayer path="layers/board/FRDM-MCXA153-MW" file="Board.clayer.yml" copy-to="board/FRDM-MCXA153" condition="myId" />
  <clayer path="board/FRDM-MCXA153" file="Board.clayer.yml" condition="myId"/>
</csolution>

[RobertRostohar]

Specifying copy-to in the pack pdsc might present some issue. Since there are no explicit rules, the pack creators could use non unique path which would result in overriding files. Should the copy-to be actually a tool option rather than specifying it in a pack?