fix: correctly construct default output filename for datasets and binary mode

[Ayush-AM]

Fixes #22

Description of changes

This PR addresses the issue where the default output filename was poorly constructed when providing a z/OS dataset name (e.g., //'my.data.set') and didn't correctly use the .bin extension in binary mode.

Key updates

• Binary Mode Support: Both the Java and C++ implementations now correctly default to a .bin extension when the -b (binary) flag is used, rather than requiring manual output specification or defaulting to .txt.
• Dataset Name Cleanup: If the input filename is a dataset path starting with // and/or enclosed in single quotes ' ' (e.g., //'my.data.set'), the tool now strips the slashes and quotes before appending the appropriate extension. This results in a clean output filename like my.data.set.bin or my.data.set.txt.
• Help Text Update: Updated the CLI usage/help text in both implementations to clarify this default filename behavior.

Testing Performed

• Built and compiled both the Java and C++ versions.
• Verified that running java -jar target/tersedecompress.jar -b "//'my.data.set'" correctly attempts to output to a sanitized file named my.data.set.bin.

[Ayush-AM]

Hi @alexgubanow,

I've opened this PR to resolve issue #22 regarding the output filename generation.

Here is a summary of the fixes implemented for both the Java and C++ versions:

• Binary Mode: When the -b flag is passed, the default output file now correctly uses a .bin extension instead of erroring out or defaulting to .txt.
• Dataset Path Cleanup: If an input dataset name is provided (e.g., //'my.data.set'), the logic now strips the leading // and surrounding single quotes (') before appending the default extension. This results in a much cleaner filename (like my.data.set.bin).
• Help Text: Updated the CLI usage text to reflect these defaults.

(Note: There was a brief issue with the DCO check due to a branch sync mismatch, but I have rebased the PR against master and the branch is now clean with a single signed-off commit).

Please let me know if everything looks good or if any further adjustments are needed!