Add regexp flag to grep and support quotes

[mattlqx]

This adds a regexp flag to the grep command in the spirit of the userland grep binary. In order to support regexps that may include spaces, supported needed added for quoting. my implementation is not very good, but it appears to get the job done including accounting for escaping.

I'm not very experienced in golang so apologies in advance.

# Standard term search
http://localhost:8888 /> grep fruit KV1/
/KV1/src/ambivalence/1> fruit = apple
/KV1/src/ambivalence/1/a> fruit = banana
/KV1/src/dev/1> fruit = apple
/KV1/src/dev/2> fruit = banana
/KV1/src/dev/3> fruit = berry

# Regex search
http://localhost:8888 /> grep fr.it KV1/ -e
/KV1/src/ambivalence/1> fruit = apple
/KV1/src/ambivalence/1/a> fruit = banana
/KV1/src/dev/1> fruit = apple
/KV1/src/dev/2> fruit = banana
/KV1/src/dev/3> fruit = berry

http://localhost:8888 /> grep [abcdef]rui[qrst] KV1/ -e
/KV1/src/ambivalence/1> fruit = apple
/KV1/src/ambivalence/1/a> fruit = banana
/KV1/src/dev/1> fruit = apple
/KV1/src/dev/2> fruit = banana
/KV1/src/dev/3> fruit = berry

http://localhost:8888 /> grep app.* KV1/ -e
/KV1/src/ambivalence/1> fruit = apple
/KV1/src/dev/1> fruit = apple

# quoted space search
http://localhost:8888 /> grep "spaced val" KV1/
/KV1/src/spaces/foo> bar = a spaced value

# escaped quoted search
http://localhost:8888 /> grep "\"quote" KV1/
/KV1/src/quoted/foo> bar = a "quoted" value

[fishi0x01]

I will merge this later today and take care of codeclimate issues before crafting a new release.

Thanks a lot for the great contribution! Highly appreciated 🙇

[mattlqx]

Thanks for taking a look. I got the codeclimate issues all taken care of. Since you liked this, I'd like to take care of being able to grep on just keys or values next.

[fishi0x01]

Thank you @mattlqx 🙇

(Reference to original Issue #59)