reset FieldContext before returning it to the pool in unpackArray

add Unpack* functions for unpacking arrays of numeric values from protobuf messages

add FieldContext.FieldByNum() for locating the field with the given fieldNum

README.md: add direct links to production code, which uses easyproto

README.md: typo fix: combiled -> compiled

reader.go: typo fix in the error message: remove superflouos `for`

add helper functions for obtaining enum values: GetEnum() and FieldContext.Enum()

added missing GetFixed32, GetSfixed32 and GetFloat functions after the commit 1e699d1348952a4b59f7da4533bf3738d68749e0

properly return false from GetString(), Getbytes() and GetMessageData() when the protobuf-encoded message misses field with the given fieldName

return easier to understand error message when the protobuf-encoded message contains unexpected wire type

Add helper functions for reading a single message with the given fieldNum from protobuf-encoded data

reader.go: add GetMessageData(src, fieldNum) function for obtaining the message data for the given fieldNum from src proto-encoded message

reader.go: fix vet error for 32-bit architectures such as GOARCH=386

README.md: mention that easyproto is used in VictoriaMetrics

clarify documentation a bit