Major update for capability analysis

[JTPetter]

• Created better GUI to select grouping by variable or manual in PCA and related functionality.
• Created GUI to select how to handle unequal subgroup sizes in PCA
• Created GUI to use stages variable in PCA.
• Implemented missing value handling for probability plot and table in process capability study.
• Implemented functionality to handle unequal subgroup sizes for control charts in process capability study.
• Implement functionality to handle missing measurement values in normal process capability tables.
• Implement functionality to handle missing measurement values in non-normal process capability tables.
• Implement functionality to handle missing values in subgroups in process capability study.
• Added option to set specification limits as physical boundaries.
• Changed selection of control charts in PCA to dropdown to improve dynamic selection based on other properties.
• Added advanced option to use different methods for estimating std. dev. in PCA.
• Fixed all capitalization and spelling.
• Added name of distribution to title of probability distribution.
• Renamed "Axis labels" to "Timestamp (optional)" in all analyses.
• Add options to display/hide distributions and specification limits in PCA plot, and add legend plus annotation.
• Display "*" instead of NA everywhere in PCA when necessary specification limits are not set.
• Added stages functionality for everything in PCA.
• Added option to select direction of bin boundary (right/left open) for histograms in PCA.
• Fixes [Feature Request - Quality Control] Add specification limits to x-mR chart in process capability study jasp-issues#2443 (Added option to display specification limits in x-mR Chart)
• Slightly moved labels of control limits to reduce whitespace (adjusted many unit tests).
• Added legend to distribution histogram in PCA.
• Fixes https://github.com/jasp-stats/jasp-test-release/issues/2508
• Making PCA more robust to many edge cases.
• Added extensive unit tests, verified with Minitab.
• Updated help file.
• Remove most ggplot2 warnings.

[JTPetter]

Most of the added lines are related to the extensive unit tests, so not quite as much to review as it might look like at first glance!

[JTPetter]

@koenderks @vandenman Do you think you might be able to take a look sometime soon?

[JTPetter]

Definitely want to include this and #297 in 0.19, ideally send out a nightly already to some people beforehand

[koenderks]

I did found one error, it error'ed for all the non-normal distributions in this case. Requires only unzip
error.jasp.zip

[JTPetter]

@koenderks Thank you, with #297 this already gives a more informative error.