Added new processors

See: #32

• <ref> now takes a JMESPath query instead. Dot notation will also work as JMESPath query.
• Added <equal> which compares 2 values, resulting in a boolean.
• Added <match> which finds a substring or matches against a regex, resulting in a boolean.
• Added <if> which takes a boolean as condition and has a then and else property.
• <switch> now is an object with on and options, rather than using additional properties in the instruction object.
• The <enrich> instruction now has an input property, rather than using additional properties in the instruction object.
• Replaced <jmespath> with <apply>. The <apply> instruction has an input and query property.
• Added <join> instruction to join strings.
• Added <replace> instruction to find / replace in a string.
• Added <numberformat> to format number using locale.
• Renamed date property of <dateformat> to input.
• Added <hash> instruction. This supports less methods.
• A <hash> instruction can have an hmac property.
• Added <encode> and <decode> instructions.
• New encode / decode methods base58 and url.
• Added <serialize> and <unserialize> instructions.
• New serialize / unserialize method url. This creates an URL Query from an object.
• Added <sum> instruction to calculate the sum of an array