Multipart File uploads

Included issues:

• guardrail-dev/guardrail#65

Contributors:

• @blast-hardcheese
• @stanislav-chetvertkov
• @sullis

Root path matcher, text/plain support

Included Issues:

• guardrail-dev/guardrail#38
• guardrail-dev/guardrail#57
• guardrail-dev/guardrail#58
• guardrail-dev/guardrail#59

Contributors:

• Devon Stewart
• Sean Sullivan

Missing `type` NPE

Included PRs:

• #55: NPE and cleanup

Contributors:

• Devon Stewart
• stanislav
• Konrad ktoso Malawski
• Alexey