Common type parser

[Fluxie]

Previously both the interface generation and type handler that generated the delegating code from Rust library interface to internal Rust had their own parsers for the types. After this commit the same type parser implementaion is used in both cases.

[codecov-io]

Codecov Report

Merging #58 into master will increase coverage by 0.26%. The diff coverage is 76.06%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
+ Coverage   76.37%   76.63%   +0.26%     
==========================================
  Files          47       48       +1     
  Lines        3069     3116      +47     
==========================================
+ Hits         2344     2388      +44     
- Misses        725      728       +3

Impacted Files	Coverage Δ
intercom-common/src/lib.rs	100% <ø> (ø)	:arrow_up:
intercom-common/src/tyhandlers.rs	93.87% <100%> (ø)	:arrow_up:
intercom-common/src/foreign_ty.rs	100% <100%> (+29.68%)	:arrow_up:
intercom-common/src/type_parser.rs	71.14% <71.14%> (ø)
intercom-common/src/generators/idl.rs	82.11% <92.3%> (-0.12%)	:arrow_down:
intercom-common/src/generators/cpp.rs	80.22% <93.33%> (-0.01%)	:arrow_down:
intercom-common/src/model.rs	89.22% <0%> (+0.02%)	:arrow_up:
intercom-common/src/guid.rs	91.47% <0%> (+0.04%)	:arrow_up:
intercom/src/guid.rs	90.75% <0%> (+0.05%)	:arrow_up:
... and 2 more

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[Rantanen]

Looks good! Thanks!