Check whether ISO-8859-1 should still be enforced for .properties files

[RandomByte]

Expected Behavior

See SAP-archive/connect-openui5#20

While this might be incompatible to current applications and libraries, we should look into it. A project setting might be already sufficient.

Current Behavior

.properties files are always served with charset ISO-8859-1 (relevant code).

Steps to reproduce the issue

1. Serve the openui5-sample-app
2. In the network trace, check the Content-Type header of the requested i18n file:
   

Context

• OS/Platform: macOS 10.13.4
• Node.js Version: v8.11.1
• npm Version: 5.8.0
• Browser (if relevant): Chrome 67
• Other information: -

Affected components

• ui5-builder
• ui5-server
• ui5-cli
• ui5-fs
• ui5-project
• ui5-logger

Stack trace/log output

[cschuff]

Since it is still Java default behaviour to expect .properties files in ISO-8859-1 I would stick to this behaviour.

Storing .properties files in any other encoding could easily break things in other (productive) enviroments. Therefore I'd prefer to fail early. This will encourage people to to store their .properties files in ISO-8859-1 and to encode special characters with \uXXXX syntax. This is what any intelligent editor would do anyways.

BTW: Files can be converted easily with Java tooling:
native2ascii -encoding UTF-8 i18n-UTF8.properties i18n.properties

[matz3]

See #168

[RandomByte]

With UI5 CLI v1.7.0, you can now configure UTF-8 as the source encoding of a projects *.properties files. The default stays at ISO-8859-1. In both cases the UI5 Tooling will escape any non-ASCII characters, so that the build result is independent from the encoding.

📖 Documentation (see propertiesFileSourceEncoding)
🔎 Demo