Add Optional Types, Fix Tool Syntax, unify file loading logic

[loukratz-bv]

Description / purpose of change(s):

fix: #95 File Loader doesn't convert to types
fix: #30 Optional Tool Input Syntax Does Not Match Custom Types
feat: #101 Let variables be optional

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
2459	1887	77%	70%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
qtype/application/_init_.py	100%	🟢
qtype/application/converters/tools_from_api.py	0%	🟢
qtype/application/converters/tools_from_module.py	90%	🟢
qtype/dsl/model.py	91%	🟢
qtype/semantic/generate.py	90%	🟢
qtype/semantic/model.py	100%	🟢
TOTAL	79%	🟢

updated for commit: 1eafbd0 by action🐍