* Prevent libcurl from inadvertently being initialized twice.
* Dynamically load libcurl only when required.
* Reduce the number of worker threads when loading footprint libraries to
prevent issues with the GitHub plugin.
1. Fixed an assumption somebody originally made in the plugin that std::string had contiguous storage. This is not specced behavior pre C++11 so we gamble by calling .reserve() which should give a far better guarantee.
2. Added copy to clipboard information for curl
3. Removed some openssl references in compiling.md
4. Renamed struct vars to be uppercase to match "public var" code style policy
* if the current select plugin is the github plugin, one can select some of these libraries and add them to the table
* if the current select plugin is the kicad plugin, one can select some of these libraries and download them to make alocal copy.
They can added to the table after they are downloaded.