Improve merge of entries with the same date

[edoardob90]

Currently, the merge_entries option allows to combine entries with the same date. Within Obsidian, the current implementation creates a few issues if using the Dataview plugin. Plus, it's not customizable.

Problems

1. The entire metadata block is kept for both entries, as well as the YAML block (there can't be two YAML metadata sections in the same Markdown file)
2. Dataview queries the multiple entry file and returns any metadata field as a list, because each field is effectively mentioned twice

Solution ideas

1. Prevent metadata fields duplication
   • A potential issue might arise when one wants to keep, e.g., the different tags or location for the entry that gets merged
2. Allow the user to choose which metadata fields are kept when merge_entries is ON
3. Have more flexibility for the separator. One idea is to have the entry's time as a separator, e.g. ## HH:MM. The user should be able to customize this template