config: implement references to nodes across YAML files

[kionz]

changes include

• refactor the config component, split implementation into several smaller source files
• move source files to src/rime/config/ directory
• implement ConfigCompiler, which processes __include and __patch in extended YAML syntax as designed by @lotem, link nodes from multiple files into a node tree in memory
• as there are shared nodes resulted from the new syntax, writing data to the node tree is now copy-on-write
• introduce ResourceResolver which maps resource (config file) references to concrete file path; allowing fallback root path

future todos:

• optional __include? and __patch? commands that do not fail if referenced resource is unavailable
• implicit patch with *.custom.yaml, mimicking the old Patcher's behavior
• __append command for list concatenation
• wildcard in patch reference, allowing adding features as downloadable module

[lotem]

Build still failing on Linux/gcc. To fix the error, use std::ofstream instead of the boost version.

[lotem]

@Prcuvu Do you know why this is happening? Does our AppVeyor config need update?
https://ci.appveyor.com/project/lotem/librime/build/master%20build%2058-wudbumll#L18

[kionz]

updated; trying ci again;

[Prcuvu]

@Prcuvu Do you know why this is happening? Does our AppVeyor config need update?
https://ci.appveyor.com/project/lotem/librime/build/master%20build%2058-wudbumll#L18

@lotem Seems that there was something wrong while establishing connection to SourceForge server (to download libboost). This happened occasionally back to when I first tested the script. Generally no changes need to be made. Rerun the build after certain amount of time seems to work.

[lotem]

@Prcuvu Understood. Thank you.

The feature LGTM. Long expected. Just a little difficult to see changes in moved files.
How about other reviewers.