Support static file mappings

[tommyy]

Proposal:

abc:
  - bar
  - baz
def:
  - foo

Will copy ./foo to server:/def/foo, and ./baz to server:/abc/baz

[petteras]

mappings:
[
{
source: "compiled/foo/*/.js",
targets: ["/var/www/min.js"],
whitelist: [],
blacklist: [],
flatten: true
},
{
source: "js/"
targets: ["", ""]
whitelist: []
blacklist: []
}
]