Tutorial: Data manipulation

[meta00]

Write a notebook to illustrate data manipulation functions, as follows:

1. One example of splitting the whole data into subsegment using time splitting both ECG and PPG.
2. A example splits data by frequency domain for ECG and PPG. Example uses different argument settings.
3. One example to trim the first and the last n-minute data.
4. One example of before and after removing the unchanged value of the n-continuous second.
5. One example of removing invalid signal data (signal = 0 and other vital signs exceed the normal range).
6. One example of removing invalid signal data using the frequency domain.

[Koaha]

Added a notebook example with the ECG data.
#TODO PPG data.
Note: Once implemented cut method, use the cut method for example 4,5,6