Opening local dapp (#4041)

* Opening local dapp

* Using Path/PathBuf instead of Strings

* Fixing typo and adding some docs to apps::fs functions

parity/cli/mod.rs

@@ -37,6 +37,7 @@ usage! {
 		cmd_snapshot: bool,
 		cmd_restore: bool,
 		cmd_ui: bool,
+		cmd_dapp: bool,
 		cmd_tools: bool,
 		cmd_hash: bool,
 		cmd_kill: bool,
@@ -525,6 +526,7 @@ mod tests {
 			cmd_snapshot: false,
 			cmd_restore: false,
 			cmd_ui: false,
+			cmd_dapp: false,
 			cmd_tools: false,
 			cmd_hash: false,
 			cmd_db: false,

parity/cli/usage.txt

@@ -5,6 +5,7 @@ Parity. Ethereum Client.
 Usage:
   parity [options]
   parity ui [options]
+  parity dapp <path> [options]
   parity daemon <pid-file> [options]
   parity account (new | list ) [options]
   parity account import <path>... [options]