feat: use cobra to provide subcommands, move sources to lib (#506)

- Use cobra in order to provide subcommands `serve` and `db`.
  - Subdir `cmd` is removed.
  - Subdir `cli` is created, which is a standard cobra structure.
- Sources related to the core are moved to subdir `lib`.
- #497 and #504 are merged.
- Deprecated flags are added. See https://github.com/filebrowser/filebrowser/pull/497#discussion_r209428120.
- [`viper.BindPFlags`](https://godoc.org/github.com/spf13/viper#BindPFlags) is used in order to reduce the verbosity in `serve.go`.


Former-commit-id: 4b37ad82e91e01f7718cd389469814674bdf7032 [formerly c84d7fcf9c362b2aa1f9e5b57196152f53835e61] [formerly 2fef43c0382f3cc7d13e0297ccb467e38fac6982 [formerly 69a3f853bd2821d2c52a435277aaac68a468d39b]]
Former-commit-id: 2f7dc1b8ee6735382cedae2053f40c546c21de45 [formerly b438417178b47ad5f7caf9cb728f4a5011a09f5e]
Former-commit-id: 07bc58ab2e1ab10c30be8d0a5e760288bfc4d4dc

build/build.sh

@@ -2,22 +2,19 @@
 
 set -e
 
-cd $(dirname $0)/..
+cd $(dirname $0)/../cli
 
-dep ensure -vendor-only
+go get -v ./...
 
 if [ "$COMMIT_SHA" != "" ]; then
   echo "Set version to ($COMMIT_SHA)"
-  sed -i.bak "s|(untracked)|($COMMIT_SHA)|g" filebrowser.go
+  sed -i.bak "s|(untracked)|($COMMIT_SHA)|g" ../lib/filebrowser.go
 fi
 
 echo "Build cmd/filebrowser"
-cd cmd/filebrowser
-CGO_ENABLED=0 go build -a
-cd ../..
-cp cmd/filebrowser/filebrowser ./
+CGO_ENABLED=0 go build -a -o filebrowser
 
 if [ "$COMMIT_SHA" != "" ]; then
   echo "Reset version to (untracked)"
-  sed -i "s|($COMMIT_SHA)|(untracked)|g" filebrowser.go
+  sed -i "s|($COMMIT_SHA)|(untracked)|g" ../lib/filebrowser.go
 fi