Time-lapse data recording and charting

**Is your feature request related to a problem? Please describe.**
I wanted to record data over multiple days and draw a chart based on this data. I can store numbers in Text record, but they cannot be used for anything else than reading right now.

**Describe the solution you'd like**
An ideal solution would be an ability to record key : value records. A new UI element would be added besides Text, Sensors, Camera and Gallery. Then the user could add multiple key and value entries. In the next phase the app could also allow arrays and nested arrays. Possible value types would be number, text, date/time (with a picker, default to current date/time).

Then there would be also a feature to plot the data on x-y scatter or line graph. Default x-axis would be time point, but it could also be changeable to any other key. Records with missing keys would be omitted.

Then also key - value templates could be created, which would simplify entry of records with the same keys.

Additionally, an ability to fill the value from sensor can be implemented.

Export to csv or text file would be also desirable.

**Describe alternatives you've considered**
I haven't thought of many alternatives yet. The feature can be implemented in stages, starting with very basic approach and then increase the complexity and richness.

**Additional context**
Possible use cases:
* Temperature logging over multiple days.
* Simple measurements, eg. growth of plants, water level, etc.
* More complex records with multiple measurements at the same timepoint.

No files, tests, or entry points are identified. Start by reviewing the existing Text, Sensors, Camera, and Gallery UI elements and decide on a narrowly scoped first stage; completion would require an agreed scope and acceptance criteria for recording and charting the data.

Written by the indexing model from the issue text.