REST API v2

- add JWT authentication
- admins are now stored inside the data provider
- admin access can be restricted based on the source IP: both proxy
  header and connection IP are checked
- deprecate REST API CLI: it is not relevant anymore

Some other changes to the REST API can still happen before releasing
SFTPGo 2.0.0

Fixes #197

windows-installer/sftpgo.iss

@@ -44,7 +44,6 @@ Source: "{#MyAppDir}\sftpgo.exe"; DestDir: "{app}"; Flags: ignoreversion
 Source: "{#MyAppDir}\sftpgo.db"; DestDir: "{commonappdata}\{#MyAppName}"; Flags: onlyifdoesntexist uninsneveruninstall
 Source: "{#MyAppDir}\LICENSE.txt"; DestDir: "{app}"; Flags: ignoreversion
 Source: "{#MyAppDir}\sftpgo.json"; DestDir: "{commonappdata}\{#MyAppName}"; Flags: onlyifdoesntexist uninsneveruninstall
-Source: "{#MyAppDir}\sftpgo_api_cli.exe"; DestDir: "{app}\examples\rest-api-cli"; Flags: ignoreversion; MinVersion: 10
 Source: "{#MyAppDir}\templates\*"; DestDir: "{commonappdata}\{#MyAppName}\templates"; Flags: ignoreversion recursesubdirs createallsubdirs
 Source: "{#MyAppDir}\static\*"; DestDir: "{commonappdata}\{#MyAppName}\static"; Flags: ignoreversion recursesubdirs createallsubdirs
 
@@ -56,7 +55,6 @@ Name: "{commonappdata}\{#MyAppName}\credentials"; Permissions: everyone-full
 [Icons]
 Name: "{group}\Web Admin"; Filename: "http://127.0.0.1:8080/web";
 Name: "{group}\Service Control";  WorkingDir: "{app}"; Filename: "powershell.exe"; Parameters: "-Command ""Start-Process cmd \""/k cd {app} & {#MyAppExeName} service --help\"" -Verb RunAs"; Comment: "Manage SFTPGo Service"
-Name: "{group}\REST API CLI";  WorkingDir: "{app}\examples\rest-api-cli"; Filename: "{cmd}"; Parameters: "/k sftpgo_api_cli.exe --help"; Comment: "Manage users, folders and connections"; MinVersion: 10
 Name: "{group}\Documentation"; Filename: "{#DocURL}";
 Name: "{group}\{cm:UninstallProgram,{#MyAppName}}"; Filename: "{uninstallexe}"