Fix #141: read all lines of version text files

[elharo]

Fixes #141

Problem

TextFileExposer only read the first line of a version text file:

String line = br.readLine();
if (line != null && !line.isEmpty()) {
    textVersions.add(line);
}

Version files with multi-line content (e.g. key=value pairs, multi-line version headers) lose all data beyond line 1.

Fix

Read all lines in a loop:

String line;
while ((line = br.readLine()) != null) {
    if (!line.isEmpty()) {
        textVersions.add(line);
    }
}

Test

Added TextFileExposerTest with two tests that build jars containing multi-line version files and assert all lines are exposed. Both fail on the old code (only first line returned) and pass with the fix.